The present invention relates to electric switches and, more particularly, to a resilient metal switching element for use in an electric switch.
U.S. Pat. No. 2,777,032 discloses a resilient switching element for use in a snap switch. As illustrated in FIGS. from 1 through 4, the switching element 1 is a unitary element stamped in one piece from resilient thin sheet metal, comprising a pair of spaced supporting legs 11, and a center leg 12 extending therebetween. The supporting legs 11 are connected to the center leg 12 by a pair of substantially semicircular loops. During installation, the supporting legs 11 are horizontally turned inwards toward each other to shorten the distance therebetween from distance X shown in FIG. 1 to distance Y shown in FIG. 2, and then the ends of the supporting legs 11 are fixedly fastened to the substrate 2. In order to let the center leg 12 to be distorted and reversed to switch on/off the circuit, a fulcrum 21 is provided engaging one side, and actuators 22;23 are provided and adapted to engage the other side of the center leg 12. U.S. Pat. Nos. 3,196,233; 2,624,819 disclose similar designs.
FIGS. From 5 through 10 shows a switching element for use in a safety switch built-in with protecting circuit constructed subject to U.S. Pat. No. 5,760,672. The switching element 3 is formed of a sheet of resilient metal having high and low heat-expansive sides. The switching element 3 has a middle leg 31 carrying one electric contact 32 for making and breaking a circuit with a stationary contact, and first and second outer legs each having one end portion connected to the same end of the middle leg 31. During installation, the outer legs are squeezed inwards toward each other to narrow the gap T1 between the free ends of the outer legs, so that the width of the mounting side is reduced from W1 to W2 (see FIGS. 5 and 6). After installation in a support 4, the switching element 3 is curved inwards/outwards, causing the middle leg 31 to move the contact 32 upwards/downwards so as to switch on/off the circuit. The switching element 3 further has a through hole 33 at the center of the connection area between the middle leg 31 and the end portions of the outer legs, which receives a push and pull rod 34 that is driven to curve the switching element 3 inwards/outwards. Further, top stop rod 35 and bottom stop rod 36 are vertically spaced from the switching element 3 at two sides, and adapted to impart a reversing force to the switching element 3. Without the stop rod 35 or 36, the switching element 3 cannot be reversed.
It is the main object of the present invention to provide a switching element, which simplifies the external arrangement of the electric switch. According to the present invention, the switching element is formed of a sheet of resilient metal having high and low heat-expansive sides. The switching element has a middle leg carrying an electric contact for making and breaking a circuit with a stationary contact on a substrate below, first and second outer legs each having one end connected to the same end of the middle leg, and an arm of width smaller than ⅓ of the width of said switching arm extended outwards from the connecting area between the middle leg and the outer legs in longitudinal alignment with the middle leg for pulling upwards/pushing downwards by an external force to reverse the middle leg.